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Discrepancies in dating scan and IVF dates

I had a dating scan at 12 weeks which put my EDD at a week ahead of the IVF/ICSI dates. At the 12 week scan, the sonographer said "it doesn't matter what your IVF dates were, this is EDD we use now". This seems a bit odd to me, since I know exactly how far along my pregnancy is because the embryologist told us when she injected the eggs! I'm 30 weeks by my dates, and 31 weeks by the dating scan.

As I'm getting closer and closer to term I've started thinking about the fact that my NHS classes me as further along than I actually am, and that I could be induced too early because of this. I'm really not keen on being induced.

I've mentioned this to the community midwife and the midwives in the antenatal clinic with not much response. Nobody knows what to say to me! I'm not even sure that they know an awful lot about IVF/ICSI and how it gives us accuracy with dates.

I am probably splitting hairs again (its not uncommon ) but is one weeks difference in EDD anything to be concerned about?

well, I guess if it means being induced then it could make all the difference for you.....
Do remember that they can't force you to be induced. If you know your true dates then you'll know, for example, that you are only 40 weeks when they say you are 41 and so there is no real reason to be induced.

I personally fail to see how a 2 dimensional image of a 3 dimensional, moving object can be more accurate than knowing when your embryo was transferred, especially when you consider the fact that its a human baby and human beings come in lots of different sizes. My hospital were adamant that a dating scan was more accurate and would consider me overdue by their date, not mine. I could never pin them down on a reference for the research or get a satisfactory explanation though. There are plenty of twin pregnancies where the babies measure differently!!! However, whe it comes to induction, they can only induce you if you turn up at hospital so if you are happy with your dates and you don't want to be induced, and you are having a healthy pregnancy and there is no indication of a problem, then stick to your guns.

This seems to come up a lot. I do not understand how hospitals can change the EDD based on rather spurious scans when ladies who have had IVF/ICSI can be so sure, so accurate, about the EDD, based on knowing when conception and transfer took place - almost to the hour! Makes no sense!

No real advice, other than to say, if you're comfortable with the EDD being the 'real' one that you know because of your treatment, then stick to your guns - don't see how they can argue really.

I have always been dated 1 day ahead by the hospital based on scans, I reckon it just means my baby is a little big for the dates that I KNOW to be accurate. I would stick with your dates for induction puposes x

My baby has always been ahead by at least a week (mostly 2) on the scans but they won't change the edd as with IVF they really do know the dates. I would stick to your guns and rely on the dates from IVF. It amazes me the significant differences in policies between hopsitals.

I am exactly the same as you - dated 1 week ahead than my IVF date. My notes and everything else is going on the 12 week date and baby has been measuring like that at every antenatal appointment. My consultant has said that if it gets to needing to be induced they'll look at both dates so I am now using the NHS date for telling everyone when I am due and reading pregnancy books (as it was getting confusing). Go with whichever date you are happy with.

I would stick with your dates, they tried to move my dates forward and I refused for much the same reasons. It seems that there is somewhat of a one dimensional view of foetuses up until 12 weeks as I was arguing with my consultant about the dates and he said "all babies are the same size at 12 weeks" so I asked him how he could say this when mine was measuring 13 weeks and I knew when they were put back, was he suggesting that my fertility clinic had invented some new method of speeding embryos up so that they are actually 2 weeks old by the time they go back - he had no answer to that.

I have to agree that I think you should stick with your original due date. Different places seem to have different policies. When we had our last scan the sonographer told me they don't change the due date because with IVF we obviously know the date of conception, so it is actually far more accurate, but she did tell me that my baby was measuring a couple of days ahead. Due date stays the same regardless here because even though my baby was measuing 18 weeks and 4 days - it was actually a 18 week and 2 day old baby. I find it a bit crazy - I mean you don't say a 3 year old is 4 because they are as tall as a 4 year old!! xxx

My clinic said it can go up to a week either way with dates for IVF babies. Some grow and multiply quicker at the begining stage.
I am sure your concerns will be listened to in regard to inducing hon.
I personaly would congratulate myself for getting to another week along & nearer to my bambino in my arms.

Just wanted to end the story I started with the dates questions. I was induced after all, but it was nothing to do with being post term. My waters broke at 39 weeks + 6 days (by my IVF dates) and I didn't deliver with 24 hours, so I was induced and delivered on 40 weeks + 1 day.

I was asked about my EDD, since there were two in my notes but I said that I'd had IVF and knew exactly when conception happened and that was it - no questions asked.